What I'm working on over summer: Heather Battles

Dr Heather Battles is spending her summer looking at polio mortality in New Zealand in the early twentieth century.

Heather's research applies a holistic, biocultural approach to understanding the evolution and ecology of infectious diseases in human populations and their impacts, both social and biological.

Multiple polio epidemics swept New Zealand in the first half of the twentieth century. Heather explains that polio is an interesting case because it "became epidemic when other epidemics were going away".

Polio was the cause of much anxiety in early-twentieth-century New Zealand because of its potential for causing paralysis, and its occurrence in the healthy and strong.

The histories of New Zealand's polio epidemics have been somewhat overshadowed by the two world wars, and the influenza epidemic that followed the First World War.

Heather is interested in exploring these marginalised pasts. The 1916 polio epidemic in New Zealand was never memorialised, and she is exploring the reasons for this.

She explains that polio epidemics tended to happen through the summer, with the New Zealand epidemics followed a few months later by epidemics in the North American summer. Although our epidemics paled in overall size to those in North America, they still featured a comparable rate of mortality.

As they developed throughout the early twentieth century, they began hitting progressively older people in bigger epidemic waves.

She says that the most popular explanation for the growth of these epidemics at this time is the hygiene hypothesis, which posits that a lack of exposure as an infant increased susceptibility to more severe polio infections later in life.

"Improvements in hygiene in the early twentieth century reduced other epidemic diseases, but broke the chain of infection."

Heather is interested in both the quantitative details of these epidemics, such as age, sex and other demographics, but is also engaging with qualitative sources such as newspapers and oral accounts from polio survivors.

Contemporary death records were separated for Māori and pākehā, so Heather is focusing on the pākehā population in her current work, and hopes to engage with iwi in the future to access Māori experiences with these epidemics.

Her research is especially relevant as New Zealand faces a resurgence in epidemic diseases that were thought to be largely eradicated, amongst similar concerns about over-crowding and hygiene in housing.